Unbalance sensing arrangement for machines having a centrifugal liquid extraction step



Aug. .23, 1960 .1 BOCHAN UNBALANCEI SENSING AR RANGEMENT FOR MACHINESHAVING Filed Aug. 4, 1958 A CENTRIFUGAL LIQUID EXTRACTION STEP FIG. 2"

INVENTOR. JOHN BOCHAN H I: ATTORNIY Aug.'23,1960 CHAN 2,950,010

J. Bo

UNBALANCE SENSING ARRANGEMENT FOR MACHINES HAVING A CENTRIFUGAL LIQUIDEXTRACTION STEP 3 Sheets-Sheet 2 Filed Aug; 4, 1958 INVENTOR. :roHNBOCHAN (bl w H [5 ATTORNEY 2,950 NES HAVING Aug. 23, 1960 Filed Aug 4.1958 J. BOCHAN UNBALANCE; SENSING ARRANGEMENT FOR MACHI A CENTRIFUGALLIQUID EXTRACTION STEP ;.'5 Sheets-Sheet 3,

INVENTOR. J'OHN BOCHAN y w M H IS ATTORNEY U sd W8 ew O UNBALAN CESENSING ARRANGEMENT FOR MA- CHINES HAVING A CENTRIFUGAL LIQUIDEXTRACTION STEP John Bochan, Louisville, Ky., assignor to GeneralElectric Company, 'a corporation of New York Filed Aug. 4, 1958, Ser.No. 752,727 12 Claims. (Cl. 210-144) This invention relates to animproved unbalance sensing arrangement, intended primarily for use inautomatic laundry machines of the typehaving a centrifugal liquidextraction step. More particularly, it relates to an improved unbalancesensing arrangement which utilizes the force of gravity acting .upon anunbalance in the type of laundry machine having a container or basketrotatable on a substantially non-vertical axis.

When an automatic laundry machine of the type having a rotating basketproceeds from a washing or rinsing step into a centrifugal extractionstep, vibration of the basket and of its enclosing tub structure maybecome quite substantial unless the clothes distribute themselves evenlyaround the basket. If this even distribution does not occur, the basketis dynamically unbalanced and, to whatever degree this condition exists,the vibration will occur. Actual harm may result to the machine fromsuch vibration; this is particularly so where, because of the increasingdemand for machines which take up a relatively small amount of spacewithout any decrease in the load capacity of the machine, the clearancebetween the parts has been cut down as much as possible.

In the type of machine having a basket rotatable on a substantiallynon-vertical axis, any unbalance in the clothes distribution within thebasket is acted on by the force of gravity. This force of gravity factorexists even before any perceptible amount of vibration has resulted fromthe unbalance. In other words, because of the gravity force, anyunbalance in the basket tends to make the rotational speed of the basketincrease when the unbalance is against the basket wall which is movingdownwardly, and to decelerate the basket when the unbalance is againstthe wall which is moving upwardly.

It is an object of this invention to utilize this gravitational etfecton the speed of rotation of the basket to provide means for sensingunbalances before any substantial vibrations have resulted therefrom.

A further object of the invention is to provide such a system incombination with'means for correcting the unbalanced distribution of theclothes in response to the gravity sensing of an unbalance ofpredetermined magnitude.

A further object of the invention is to provide an improved washingmachine of the type having a centrifugal liquid extraction cycle inwhich substantial vibrations during extraction are prevented by agravity sensing system operative at or slightly above the speed at whichthe clothes become plastered around the periphery of the container.

A further object of the invention is to provide such a machine wherein,upon the sensing of an unbalance, the speed of the machine is decreasedbelow centrifugal speed to permit redistribution of the clothes, and isthen returned to the sensing speed.

In one aspect of my invention I-provide, in a washing machine, a clothescontainer or basket rotatable on a substantially non-vertical axis.Multi-speed drive means are provided for rotating the basket. The drivemeans includes a drive member which is positioned to engage a portion ofthe basket so that operation of the drive member rotates the basketportion to drive the basket. The

2,950,010 Patented Aug- "5 953? ,2 engagement of the drive member thebasket portion is of the type which permits accelerations of thecontainer portion other than those impartedfrom the drive member- Thedrive means rotates the basket at a relatively low speed for washingclothes in the container, and at a relatively high speed whencentrifugalextraction of liquidfrom the clothes in the container is desired. Thebasket is responsive to the force of gravity acting onany' unbalancetherein to provide intermittently a torque tending to accelerate thebasket portion above the speed of the driving member. To give a specificinstance of this, if the drive member is pushing the basket portionaround in its rotary path at a speed sufiicient to plaster the clothesaround the basket, then in response to 'a descending balance in thebasket it will tend to accelerate ahead of the drive member. I

This phenomenon is made'use of by providing means, responsive to'apredetermined amount of gravity-caused accelerating torque on'thecontainer portion, for slowing the clothes basket below centrifugingspeed. In this manher, a high speed operation with an undesirableamountrof clothes unbalance in the basket is precluded at all times.

The features of my invention which I' believe to be novel are set forthwith particularity in the appended claims. My invention itself,'however,may best be understood by the following descriptionjtaken in conjunctionwith the accompanying drawings.

In the drawings:

Fig. 1 is a side elevational view of a domestic laundry machineincorporating one embodiment of my improved unbalance sensingarrangement, certain surfaces of the view being broken away in orderbetter to illustrate details;

Fig. 2 is a rear elevational view of the machine of Fig. 1;

Fig. 3 is a rear elevational view of alaundry machine including a secondembodiment of my improved unbalance sensing means, certain surfacesbeing broken away to illustrate details; f

Fig. 4 is a rear elevational view of a laundry machine including a thirdembodiment of my improved unbalance sensing means, certain surfacesbeing broken away to illustrate details; and

Fig. 5 is a simplified schematic diagram of a circuit suitable for usewith the construction of Fig. 4.

Referring now to Figs. 1 and 2, I have shown my invention in one form asapplied to a domestic washing machine 1 which includes an outer cabinet2 mounted on a supporting base structure 3. Access-to the machine forloading. and unloading of clothes may be provided by a door (not shown)disposed in the front wall 4 of the cabinet. Abacksplasher 5 mounted atthe top of the cabinet serves as a mounting means for suitable operatorcontrols for the machine, such as, for instance, rota'table dial 6. 1

The machine 1 is of the type which includes a clothes basket rotatableabout a non-vertical axis; specifically, it includes a perforated basket7 which is disposed for rotation about a horizontal axis. Basket 7 ismounted within an imperforate tubstructure 8 which encloses it on allsides, and is rotatably supported from. the tubnstructure by ahorizontally extending shaft 9 (Fig. I) mounted in an elongated bearing10 hung from the rear wall 11 of the tub structure. The shaft 9, as wellas supporting the basket, also serves as a means for turning it duringoperation of the machine. The tub and basket are generally provided withopenings (not shown) suitably'aligned with the opening in wall 4 topermit clothes to beplaced into or removed from the basket. Y

Tub 8 is supported from base 3 bymeans of a plurality of brackets orarms'12 which are mounted on upstanding plates 13 fixedly attached to base3. While arms 12 can be secured directly to the wall of tub 8, they mayalso be attached thereto by means of suitable brackets 14 as shown (Fig.2).. During the operation of the machine, basket 7 is'driven fromelectric motor 15 through a drive including a pair of flexible belts 16and 17. Belt 16 connects the output pulley (not shown) of motor 15 tothe input pulley (not shown) of a multispeed transmission assembly 18.Belt 17 connects the output pulley 19 of transmission assembly 18 to abasket drive pulley 20. The basket drive pulley 20 in turn imparts therotation to basket 7 through a construction which is further describedherebelow in specific connection with the illustrated embodiments of myinventive concept.

Machine 1 includes the other components normally provided in connectionwith domestic washing machines. Thus, for instance, the water supplymeans, whereby the water is admitted to and discharged from tub 8, mayinclude connections 21 and 22 through which hot and cold water issupplied to the machine for the washing operation. A valve controlled bya solenoid 3 admits hot water to the machine and a valve controlled bysolenoid 24 admits cold water to the machine. The hot and cold watervalves under the control of the solenoids 23 and 24 discharge to acommon outlet conduit 25, through a suitable air gap, and into funnel 26which discharges into a line 27 leading to the interior of tub 8 througha suitable connection 2.9. The air gap provided by funnel 26 makes itimpossible for water to be syphoned from the machine so as tocontaminate the incoming water supply line. A pressure actuated waterlevel control 30 connected to the interior of the tub 8 by a line 31controls both solenoids 23 and 24 to maintain the proper water level inthe machine during the washing operation. The wash and rinse water usedduring the washing operation is discharged from the machine through asump 32 mounted at the bottom of the tub. A suitable discharge hose 33leads from the sump to a motor driven drain pump 34 which discharges tothe household drain through a suitable conduit such as hose 35.

With the apparatus shown, any suitable sequence derived from the basicsequence of washing, rinsing and spinning may be utilized to effect thewashing operation. Transmission 18 is arranged so that it is capable ofrotating pulley 20 at a speed appropriate to effect rotation of basket 7at approximately 47 rpm, for instance, for a washing operation and at asuitable high speed, generally substantially upward of 200 rpm, for thecentrifugal liquid extraction operation. Transmission 18 is alsodesigned to provide yet a third speed for basket 7; this third speedmay, where the usual 26 inch diameter basket is provided, he on theorder of '70 revolutions per minute, which is slightly above the minimumspeed at which all clothes in the basket are under the influence ofcentrifugal force and plastered against the basket wall.

In order to achieve rotation of basket 7 by transmission 18, pulley 20is rotatably mounted on an end 36 of shaft 9 extending from the rearWall 11 of tub 8. Pulley 20 includes a projecting portion 37 which is indriving relationship to an arm 38 secured to shaft end 36 so as torotate therewith. Since shaft 9 constitutes a driving connection tobasket 7,, rotation of pulleyml in a counterclockwise direction (asviewed in Figure 2) causes driving member 37 to engage the end 39 ofprojecting arm 38 from behind relative to the direction of rotation, andthrough that arm and shaft 9 to rotate basket 7.

It will be noted that if the clothes load within basket 7 should beunbalanced, then at the time that the extra weight is descending on theleft hand side of the basket (Fig. 2) the unbalance will give the basketa torque tending to accelerate it ahead of drive member 37 on pulleyconstruction of the type illustrated and described, substantially beforethere are any noticeable unbal nce libidtions. The tendency of arm 38 toaccelerate ahead of driving member 37 constitutes an indication ofunbalance which may cause harmful vibration if not corrected.

To take advantage of this signal, suitable means are provided forcausing the basket 7 to decelerate below centrifuging speed in responseto a predetermined angular displacement of :the basket ahead of thedriving member 37. In the embodiment of Fig. '2, this means is providedby spring 40 secured at one end to a pin 41 on pulley 20 and at itsother end to pin 42 on basket arm 38. As soon as the angulardisplacement between driving member 37 and arm 38 becomes great enoughso that spring 40 is moved over center, as represented by shaft end 36,the force of the extended spring will exert a-torque causing arm 38 onbasket 7 to spin around at increased speed aheadof driving member 37.Arm 38 thus moves around so, that it-is almost a full circle ahead ofthe driving member 37; consequently, since there is no longer anyoperative connection between pulley 20 and basket 7 the basket starts toslow down. The basket continues to slow down .until driving member 37catches up with arm 38 to start once again to push it in its rotationalpath.

20. This phenomenon occurs, with a washer .It is contemplated thatduring the sensing operation described, the transmission will berotating the basket at plaster speed, i.e., at the minimum centrifugalspeed. Therefore, the decrease in rotational speed of the basket causessome of the clothes to .cease to be held by centrifugal force, and someredistribution of the clothes within the basket 7 takes place. Ifthisredistribution effects substantial balance within the basket, then therewill be little or no tendency for arm 3.8 to move .angularly ahead ofdriving member 37. If, however, there is still an undesirable amount ofunbalance present when member 37 again starts to drive arm 38, the armwill again move ahead of the driving member until spring moves overcenter, at which time the entire cycle will be repeated. Thus, theconstruction described senses .undesirable unbalance at the minimumcentrifugal speed, where the vibrations are still so small as to benegligible, and causes the unbalance to be corrected before a higherspeed is attained. After the sensing operation is complete, thetransmission is caused. to provide the high speed spin for centrifugalliquid extraction. This may be done, for instance, in the usual way byproviding a standard timer control which allows a predetermined timeinterval for the sensing operation, and thereafter provides theextraction operation.

Referring now to Fig. 3 a secondembodiment of the invention will bedescribed, using like numerals for like parts. In this embodiment thepulley 43 which is driven by transmission 18 through belt 17 has anannular groove 44. As before, the pulley 43 is mounted to rotate freelyon end 36 of the basket shaft.

An arm 45 is secured to rotate with shaft end 36. Arm 45 .has anextension part 46 terminating in a'projecting portion 47 which ispivotably mounted on a pin 48 secured on arm 45. A spring: 49 having oneend secured about a pin 50 and its other end secured in an opening 51 ofextension part 461s arranged to bias the extension part about pin 48 sothat proiecting portion 47, which extends into the annular groove 44 ofpulley 46 has the position shown. e

Pivotally-mounted on" a pin 52 secured on pulley 43, there is anirregularly shaped member 53 having a curved underside 54 and a curvedupper side 55 which intersect each other to form the sharp end of member53. The other end ofmember 53 is formed as a concavely curved portion56. A spring 57 is provided, secured at one end on a pin 58 extendingfrom pulley 43 and at its other end on a pin 59 extending from member53. Spring 58 serves to bias member 53 either to the position shown infull outline or to the position shown in phantom outline, i.e., i p l s.i ermed a ,PQ i H Wilt motor .15 causes rotation of pulley 43 in acounmitting a high spin speed, the cycle will be repeated, with thespeed being returned to tumble for redistribution of the clothes andanother attempt at the intermediate speed being made.

It will be seen that this third embodiment, as set forth in Figs. 4audS, provides a construction which is responsive to a very small amountof angular movement of the basket relative to the pulley, With a torquedifferential being substituted for the relatively large angular movementrequired in the embodiments of Figs. 2 and 3. It will further beobserved that the roller construction set forth in the embodiment ofFig. 4 provides quiet operation of the construction by preventing impactbetween relatively moving parts.

It will be seen from the foregoing that my invention provides aconstruction whereby the gravitational effect on an unbalanced load in abasket rotating on a generally horizontal axis is utilized to provide anindication of the need for redistribution of the clothes. It willfurther be seen that this is achieved before any harmful vibrations canoccur as a result of an increase to a relatively high speed with theunbalance still present.

While in accordance with the patent statutes I have shown what atpresent are considered to be the preferred embodiments of the invention,it will be obvious to those skilled in the art that various changes andmodifications may be made therein without departing from the invention,and I therefore aim by the appended claims to cover all such changes andmodifications as fall within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. In a laundry machine, a clothes basket rotatable on a substantiallynon-vertical axis, multi-speed drive means for rotating said basketincluding a drive member positioned to rotate substantially coaxiallywith said basket, said basket having a portion. engageable by said drivemember, said drive member engaging said basket portion to rotate saidbasket at a relatively low speed for tumbling clothes in said basket andat a relatively high speed for centrifugal extraction of liquid from theclothes, said basket portion being angularly movable away fromengagement with said drive member by the force of gravity in response tounbalanced distribution of clothes within, said basket; and meansresponsive to a predetermined angular movement of said basket portionrelative to said drive member for decreasing the basket speed forredistribution of the clothes.

2. The apparatus defined in claim 1 wherein saiddrive member engagessaid basket portion from behind relative to the direction of rotation,said drive member pushing said basket portion around to eflfect thedriving of said basket, said basket portion being angularly movableahead of said drive member in the direction of rotation by the force ofgravity in response to unbalanced distribution of clothes within saidbasket.

3. In a laundry machine, a clothes basket rotatable on a substantiallynon-vertical axis; multi-speed drive means for rotating said basketincluding a belt driven pulley positioned to rotate substantiallycoaxially with said basket, a drive member secured on said pulley torotate therewith, a shaft secured to rotate with said basket, an armsecured to rotate with said shaft, said arm being engageable from behindrelative to the direction of rotationby said drive member, said drivememberpushing said arm in a rotary path at a relatively low speed fortumbling clothes in said basket during washing operations and pushingsaid arm at a relatively high speed for centrifugal extraction of liquidfrom the clothes in said basket, said basket being subject toacceleration by the force of gravity in response to unbalanceddistribution therewithin, said' arm being angularly movable ahead ofsaid drive member in response to acceleration of said basket by theforce of gravity; and means responsive to a predetermined angularmovement. of. said basket arm ahead of said: driving member fordecreasing the basket for redistribution of the clothes. p

4-. The apparatus defined in claim 3 wherein said drive means rotatessaid basket just fast enough to plaster the clothes around said basketsubsequent to the washing operation, said means responsive to apredetermined angular movement of said basket arm first slowing saidcontainer below plaster speed to eifect redistribution of the clothesandthen causing engagement of said basket arm by said drive member forfurther rotation at plaster speed.

5. In a laundry machine, a clothes basket rotatable on a substantiallynon-vertical axis; multi-speed drive means for rotating said basketincluding a pulley rotatably mounted substantially coaxially with saidbasket; a drive member secured on said pulley; a shaft coaxially securedto said basket to rotate therewith; an arm extending" radially from saidshaft and secured thereto; said arm being engageable by said drivemember from behind relative to the direction of rotation of said drivemember, said drive member engaging said arm to rotate said basket at arelatively low speed for washing clothes in said basket, at a relativelyhigh speed for centrifugal extraction of liquid from the clothes, and atan intermediate speed just high enough to plaster the clothes about saidbasket by centrifugal force for unbalance sensing, said basket beingsubject to acceleration and deceleration in response to the force ofgravity on unbalanced loads within said basket during its intermediatespeed rotation, said arm being angularly movable" ahead of said drivemember in response to basket acceleration by the force of gravity; andmeans responsive to a predetermined angular move ment of said arm aheadof said drive member for slowing said basket below said intermediatespeed for redistributing the clothes, said responsive means comprisingan over-center spring secured at one end to said pulley and at' the"other end to said and, said spring being positioned so that upon saidpredeterminedangular movement of said arm said spring passes over the'center of rotation of said arm whereby said spring pulls said arm aroundahead of said pulley until it is substantially one full revolution aheadthereof, said basket then being free to slow down below saidintermediate speed for redistribution of the clothes during the periodin which said drive member is catching up to said arm, said drive memberagain pushirig said arm in a rotary path at said intermediate speedafter it catches up.

6. In a laundry machine, a clothes basket rotatable on a substantiallynon-vertical axis; rnulti-speed drive means for rotating said basketincluding a drive member,

said basket having a portionengageable by said drive member, said drivemember engaging said basket portion so as to permit accelerations ofsaid basket portion other than those caused by said drive member, saiddrive member engaging said basket portion to rotate said container at arelatively low speed for washingclothes in said container andat arelatively high speed for centrifugal extraction of liquid from theclothes, said basket being responsive to the force of gravity acting onan unbalanced distribution of clothes Within said basket to provide atorque tending to move said basket portion ahead of said drive member;and means responsive to a predetermined amount of said torque fordecreasing the basket speed sufliciently to effect redistribution of theclothes.

7. In a laundry machine, a clothes basket rotatable on a substantiallynon-vertical axis; multi-speed drive means for rotating said basketincluding a' drive member positioned to rotate substantially coaxiallywith said basket, said basket having a portion engageable by said drivemember, said drive member engaging said basket portion to rotate saidbasket at a relatively low speed for washing clothes in said basket, atan intermediate speed just sufficient to plaster clothes around saidbasket by centrifugal force for sensing unbalances, and at a relativelyhigh speed for centrifugaiext-r-action ofliquid from the clothes, saidbasket being responsive to the force of gravity acting on clothesdistributed in an unblanced fashion within said basket to provide atorque tending to move said basket portion ahead of said drive member,said drive member driving said basket at said intermediate speed for apredetermined period before going from said low speed to said highspeed; and means responsive to a predetermined angular movement of saidbasket portion relative to said drive member during said intermediatespeed drive for slowing said basket sufiiciently to effectredistribution of the clothes.

8. The apparatus defined in claim 7 wherein means are provided to causerotation of said basket by said drive member at said intermediate speedagain after a predetermined period of rotation at clothes distributingspeed in response to actuation of said responsive means.

9. In a laundry machine, a clothes basket rotatable on a generallyhorizontal axis, multi-speed drive means for rotating said basketincluding a belt driven pulley positioned to rotate substantiallycoaxially with said basket, a drive member secured to said pulley torotate therewith, a shaft coaxially secured to said basket to rotatetherewith, an arm secured to said shaft to rotate therewith, saiddrivemember being arranged to engage said arm on the back side thereofwith respect to the direction of rotation, said drive member engagingsaid arm to rotate said basket at a relatively low speed for washingclothes in said basket, at a relatively high speed forcentrifugalextraction of liquid from the clothes, and at an intermediatespeed just sufficient to plaster the clothes around said basket bycentrifugal force for sensing unbalances, said pulley having an annulargroove formed therein, a projecting portion on said arm biased to aposition where it is arranged to rotate around in said groove, saidpulley having a recess formed radially inward of said groove arranged toreceive said projecting portion to be in driving relation thereto, and amember movably secured to said pulley adjacent said pulley recess, saidmovable member being biased to two alternative positions, said movablemember guiding said projecting portion past said recess around in saidannular groove in one of said positions, said movable member guidingsaid projecting portion out of said groove and into said recess in theother of its positions, said arm being angularly movable ahead of saiddrive member by the force of gravity in response to unbalanceddistribution of clothes within said basket during said intermediatespeed drive, said projecting portion being responsive to a predeterminedangular movement of said arm relative to said pulley for moving out ofsaid recess into said groove whereby said basket starts to slow down topermit redistribution of the clothes therein, said projecting portionrotating around in said annular groove in a direction opposite to thedirection of rotation of said pulley during said slowing down, saidmovable member being positioned to guide said projecting portion pastsaid recess for a second revolution in said annular groove the firsttime said projecting portion engages said movable member, saidprojecting portion in being so guided moving said movable member to itsother alternative position, said movable member after the secondrevolution of said projecting portion guiding said projecting portioninto said recess for a resumption of the driving relationship of saidpulley and said basket, said projecting portion in moving into saidrecess forcing said movable member back to its one position in readinessfor another redistribution cycle.

10. In a laundry machine, a clothes basket rotatable.

on a substantially non-vertical axis; multi-speed drive means forrotating said basket including a drive member positioned to rotatesubstantially coaxially with said basket, said basket having a portionengageable by said drive member, said drive member engaging said basketportion to rotate said basket at a relatively low speed for washingclothes in said basket, at a relatively high speed for centrifugalextraction of liquid from the clothes, and at an intermediate speed justabove that necessary to plaster the clothes about said basket bycentrifugal force, said basket being subject to torques resulting fromthe force of gravity acting on clothes distributed in unbalancedrelationship within said basket, and means responsive to a predeterminedamount of gravity-caused torque on said basket portion when said basketis being driven at said intermediate speed for slowing said basket belowsaid intermediate speed for redistribution of the clothes, saidresponsive means comprising an electrical contact secured on said drivemember, a second electrical contact secured on said basket portion, saidcontacts being movable relative to each other to open and closedpositions, said contacts assuming one of said positions when the torqueresulting from the force of gravity is below a predetermined value andassuming a second position when the torque resulting from the force ofgravity is above the predetermined value, movement of said contacts fromsaid one position to said second position controlling a circuit forslowing said basket below centrifuging speed for redistribution of theclothes, the slowing of said basket returning said contacts to theirfirst position, and a circuit controlled by said contacts in their firstposition to return the speed of rotation of said basket to saidintermediate speed for another unbalance sensing operation.

11. In a laundry machine, a clothes basket rotatable on a substantiallynon-vertical axis; multi-speed drive means for rotating said basketincluding a belt driven pulley positioned to rotate substantiallycoaxially with said basket, a drive member secured on said pulley torotate therewith, a shaft secured coaxially to said basket to rotatetherewith, an arm member secured to said shaft to rotate therewith, saidarm being engageable by said drive member from behind with respect tothe direction of rotation of said drive member, said drive memberengaging said arm to rotate said basket at a relatively low speed forwashing clothes in said basket, at a rela tively high speed forcentrifugal extraction of liquid from the clothes, and at anintermediate speed sufiicient to plaster the clothes around the wall ofsaid basket by centrifugal force, said basket being subject to torqueresulting from the force of gravity acting on clothes distributed inunbalanced relationship within said basket, said torque acting in adirection to tend to move said arm angularly ahead of said drive member,spring means secured between said pulley member and said arm member andbiasing said arm member into engagement with said driving member, saidtorque becoming greater than the biasiug force upon a predetermined sizeof unbalance at said intermediate speed thereby to cause movement ofsaid arm member ahead of said driving member, electrical contact meanshaving a first relationship when said driving member engages said armmember and having a second relationship when said torque overcomes thebiasing force, and a circuit including said contacts, said circuitcontrolling the speed of operation to cause return of the speed to saidlow speed in response to movement of said contacts to said secondrelationship and causing return of said speed to said intermediate speedin response to return of said contacts into said first relationship.

12. The apparatus defined in claim 11 wherein said contacts areelectrically connected in said'first relationship and are electricallyseparated in said second relationship.

References Cited in the file of this patent 0 UNITED STATES PATENTSBochan et a1. Oct. 1, 1957

